Arroyo-Currás, N.

Eden, Alexander

Eijkel, Jan C.T.

Pennathur, Sumita

satik, yesil

Scida, K.

Here we show, for the first time, the ability of nano-confined bipolar electrodes (BPEs) to preconcentrate and deplete charged fluorophores in the absence of voltage bias. Typically, bipolar electrochemistry has been studied in relation to preconcentration techniques, where a combination of applied voltage bias and pressure driven flow concentrates ions in the proximity of a BPE. A thorough study of what happens after the voltage is turned off, however, has never been performed because any resultant electrokinetic effects are masked when the dimensions of the system are µm-sized. At the nanoscale, in contrast, the tight confinement of the solution surrounding the BPE generates unique ion transport phenomena after the voltage bias has been removed. Here we investigate these phenomena by polarizing BPEs in the presence of an electric field, thus creating areas of highly positive and negative charges that, depending on ionic charge, drive ion repulsion from and attraction to the BPE poles. By holding the voltage bias high enough to drive the water splitting reaction, we generate H+ and OH- ions that affect the fluorescence emission of the fluorophore. When we remove the bias, the BPE surface becomes neutral, leaving the surrounding solution with a charge imbalance. We hypothesize that this imbalance is immediately neutralized by fast ion transport, yielding localized areas of fluorescence enrichment and sharp pH-induced fluorescence gradients. We experimentally demonstrate the validity of this hypothesis by studying the (1) responses induced by different fluorophores, (2) preconcentration/depletion efficiencies at different ionic strengths and biases, and (3) effect of confinement in the overall response of the system

Scida, Karen

Arroyo-Currás, Netzahualcóyotl

Satik, Yesil

NARCIS 

Bipolar electrode-induced electrokinetic effects in nanochannels generate fluorescence enhancement and sharp pH gradients in the absence of a voltage bias

University of Twente Research Information

Bipolar electrode-induced electrokinetic effects in nanochannels generate fluorescence enhancement and sharp pH gradients in the absence of a voltage bias

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University of Twente Research Information